Q1. An aluminum cup contains 225 g of water and a 40-g copper stirrer, all at 27°C. A 400-g sample of silver at an initial temperature of 87°C is placed in the water. The stirrer is used to stir the mixture until it reaches its last equilibrium temperature of 32°C. Analyse the mass of the aluminum cup.

Q2. A potter's wheel having a radius 0.50 m and a moment of inertia 14.3 kg•m2 is rotating freely at 51 rev/min. The potter can stop the wheel in 5.0 s by pressing a wet rag against the rim and exerting a radially inward force of 66 N. Find out the effective coefficient of kinetic friction between the wheel and the wet rag.